A first aspect of the present invention relates to a vessel adapted to perform subsea wellbore related operations and a method for performing such subsea wellbore related operations, in particular including module handling and laying flexible pipeline, e.g. wellbore intervention.
Such “wellbore intervention vessels” are well known and commercially available for years, e.g. from the applicant. In general, these are light-weight vessels provided with a moonpool and having a stationary drilling mast having a closed contour adjacent said moonpool. Such a closed contour drilling mast is of a relatively light-weight construction.
In order to handle modules, one or more vertical trolley rails are provided at a front side of the drilling mast, extending into the moonpool and along a mast side moonpool wall part. A module handling trolley is provided which is—during module handling—movable along the vertical trolley rails in a vertical trolley path into the moonpool, and a hoisting device is adapted—during module handling—to lower and raise the module and/or the module handling trolley.
In common embodiments, a module handling device is provided which is adapted to—during module handling—transfer modules to the module handling trolley. The module handling device comprises skid rails on the main deck extending towards the moonpool wall. During module handling an unobstructed module handling area is provided above the skid rails and the moonpool.
In known embodiments wherein the drilling mast is a “multi-purpose tower” as known from the applicant, the drilling mast is adjustable for pipelay operations, by installing accessories such as tensioners to the multi-purpose tower.
In known embodiments, one or more tensioners are installed onto the drilling mast, each tensioner comprising a tensioner frame supported by the drilling mast and multiple tracks supported by said tensioner frame, said tracks being adapted to—in a pipeline laying configuration during laying flexible pipeline—engage the flexible pipeline and to support at least part of the weight of a launched pipeline in a firing line which extends on the outside of and adjacent to the front side of the drilling mast and through the moonpool.
Hence, although the known vessels provided with a multi-purpose tower are able to perform both module handling operations and laying flexible pipeline, this requires the installation and de-installation of tensioners. In view of the dimensions and weight of such tensioners, this is a time-consuming process.